How does everything you just said differ or overlap with neuropathic pain or that sort of burning pain that I'm sure some people are familiar with? Certainly I was familiar with it for several years. Yeah. Um is that simply a subset of this? Are there various different types of pain that don't have a clear um cause effect relation to tissue damage? Yeah. So we have different ways of categorizing pain, putting it into different buckets, if you will. Um, one is no susceptive pain. And you'll note that that word no susceptive sounds very similar to noceptors and it's by design. It means that it is pain caused by activation of primary noceptors, whether it be in your skin or soft tissues or viscera. And it tends to have certain qualities. It's very easy to localize. Uh you know exactly where it is. It has a certain intensity. That no susceptive pain tends to be timelmited. Responds well to short-term use of analesic agents. Uh acetaminophen uh NSAIDs, COX 2 inhibitors, uh opioids and it tends to go away. And this is the kind of pain that occurs after typically acute injuries. You then have visceral pain which as a former general surgeon you understood this. This is due to activation of those primary noceptors in our visca. Now the difference and why we bring up the distinction with visceral pain that is either in our thoracic viscera or abdominal or pelvic visca is that the receptive fields that means where those noiceptors serve and what we perceive are very diffuse and wide. When you get a stomach ache you can't put your finger exactly where it hurts. you tend to put your whole hand over it and say, "I'm kind of it hurts here. It's diffuse." That's because the brain, the spinal cord and the brain have these diffuse receptive fields which expand the area. The viscra don't typically respond to the same type of stimuli that uh no susceptive pain does. You'll remember when you were taking a boi um to the bowel, the small intestine, patients wouldn't normally move because the noiceptors don't respond to that. But if you tug on it, if you pull that or inflate it or inflate it, boy oh boy, blood pressure goes up, heart rate goes up. Um interesting characteristics with visceral pain is there's something called viscosmatic convergence meaning that the afference the information coming in from the gut from the uh thorax converge with the same sensory systems from the rest of our different parts of our body. So um you know you may remember the old medical school adage uh C345 keeps the diaphragm alive. Okay we all we all had these in in med school. Well that means that the third fourth and fifth cervical nerve roots subserve our diaphragm which help us breathe. When the general surgeons or others are operating and they get blood under the diaphragm it irritates the diaphragm. And what patients will typically complain of shoulder pain because the shoulder is subserved by the fourth and fifth cervical areas. And so when they had shoulder pain, the answer wasn't, you know, something's wrong with their shoulder. It's they had some irritation of blood under there. It's why when people have a heart attack, pain radiates out into the arm because you've got the upper thoracic nerves subserving the heart that overlap with the nerves that go down your arm and the nervous system gets confused and that's how it's expressed. And if you like the neurosciences, it's all pretty cool. If you're experiencing it, not so cool. Let's get to neuropathic pain. And by the way on visceral pain what is the response to treatments with respect to the way we saw in noceptive pain where hey great response to these NSAIDs or opioids or whatever. Yeah typical analesics can be helpful um but identifying visceral specific anti-nosceptive drugs is still an area of hot research. Um these days it's more about trying to identify the causes of visceral pain and you know reducing substances that are winding those noceptors up. Neuropathic pain another bucket neuropathic pain means injury to either the peripheral or the central nervous system. The nerves out in the body it's either injury or dysfunction too. nerves out in the body or the nervous system in your spinal cord or in your brain. Classic, you know, you know, you get nerve injury from a trauma, from surgery. Um, classic qualities people describe burning, sharp, lancinating, stabbing, shockike. Um, this is the kind of pain that some people tragically get after a theamic stroke in their brain. You know, half their body is just like terrible burning pain and it and just there's nothing going on out here. It's all central. Um, this is the kind of pain that you get and you experienced with ridicular pain. And ribbicular pain means uh in this case injury to a nerve root coming out of your spine. It's this sharp radiating pain if you've got it in your lower back that radiates down in down your leg typically below your knee into your foot. This can be very challenging to treat with common analesics. We tend to draw upon different categories of medications for this. These are, broadly speaking, anti-neuropathic pain drugs. Um, and here in our field, we steal from everybody. You know, there's only a few FDA approved medications for pain, like a handful. So what we've learned to do is to steal borrow drugs from the neurologists, their anti-convulsants, their anti-seizure medications, the uh gabapentonoids, the taggls and their derivatives, their other anti-seizure medications because they tend to have mechanisms of action that also work on nerves. pain. Gabapentan, I think you've had perhaps some experience with. Um, turns out it's a lousy anti-seizure drug. Terrible, but it's a pretty good, you know, anti- nerve pain drug. Four grams a day. Four grams a day. I was awfully drowsy, though. You know who gets credit by the way for making uh I give credit to uh making gabapentin the blockbuster drug? George Clooney. How you ever watched ER? Uh yeah. Yeah. Yeah. He was a pediatric ER doc. That's right. Kid comes into the ER with a skateboarding injury. Um George Clooney puts the kid on gabapentin. Now where that had all started was a case report from a couple of ED docs who had noted by putting people on gabapentin that their acute pain got better. So I felt like beforehand when I was practicing medicine around the time I saw you practicing pain medicine that I'd look like a genius if I put somebody on gapentin because nobody heard of it. And then after that came out floodgates open primary care docs started using it. Now everybody's tried it and it's a very safe medication. I have I should also make a mention when I'm talking about these meds or any treatments. I have zero industry relations with anybody. Nobody. I don't take any industry money. You can go look me up on open payment CMS which is a public database. Okay. Neuropathic pain. There's another one. There's a new kit on the block called no plastic pain. I don't know if this one is uh made much traction yet. This is a newly introduced category of pain which is thought to represent dysfunction in the central pain processing system. And I'm not precisely defining it, but that's the gist of it. It means that in the in the absence of an identifiable peripheral cause there is dysfunction in the brain and the spinal cord that is causing pain perpetuating and amplifying pain. noslastic pain and it has been tied in with conditions like fibromyalgia, temporalmandibular disorders, uh some aspects of chronic low back pain, uh irritable bowel syndrome, interstitial cyitis, uh and more. It it's slowly starting to get traction. So when we when we talk about pain both to study it but also ideally to treat it we put them in these categories that we just described. Yeah. I was about to say before you gave your examples I was going to say no plastic pain must be a huge bucket because it's everything for which we don't understand one of the three. It's sort of the all else bucket which is enormous especially for chronic pain. Right. You're absolutely right and I think the verdict is still out in the end. Does no plastic pain stick around or is the problem that in these conditions that we associate with no plastic pain, medical science hasn't caught up to identify a specific peripheral driver. I'm of the opinion it's that latter. Like I think we're gonna find peripheral drivers for fibromyalgia. There's some controversy right now as to whether fibromyalgia represents a small fiber neuropathy. Um and just because we may not be able to identify a lesion doesn't mean that there's not something there. But as in all things, the truth will weigh out and uh we'll see how the story plays. [Music]